Single use circuit breaker



1956 K. v. MATTSSON ETAL 3,277,255

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ATTORNEYS United States Patent 3,277,255 SINGLE USE CIRCUIT BREAKERKjell Valentin Mattsson, Karlskoga, and Axel Erik Ludvig Olsson, Bofors,Sweden, assignors to Aktiebolaget Bofors, Rotors, Sweden, 2 Swedishcompany Filed Oct. 16, 1964, Ser. No. 404,406 Claims priority,application Sweden, Oct. 22, 1963, 11,578/ 63 2 Claims. (Cl. Mill-61.08)

The present invention relates to an electric circuit breaker and, moreparticularly, to a circuit breaker which is to be used only once.

Circuit breakers of this type may be used on missiles and particularlyin rocket type missiles for breaking a circuit therein at apredetermined time, or in response to a control signal. Morespecifically, the circuit breaker may be advantageously used on missilescarrying several electrically ignitable tracers. With missiles of thistype it is often desired to ignite all the tracers on the missiles, oronly selected ones. For such use, the circuit breaker is connected withthe energizing circuits for the ignition devices of the tracers so thatthe circuit breaker when operated interrupts the energizing circuits forthe nonselected tracers so that the same remain inactive. Actuation ofthe tracer circuits may be conventionally controlled by a timing deviceor a selector transmitting a control signal to the circuit breaker.

It is a broad object of the invention to provide a novel and improvedcircuit breaker of the general kind above referred to.

A more specific object of the invention is to provide a novel andimproved circuit breaker of the general kind above-referred to which issimple, rugged and inexpensive in construction in that the circuitbreaker does not include any delicate parts which are likely to bedamaged by the heavy jars and rapid acceleration to which a missile isunavoidably subjected when launched.

Other and further objects of the invention will be pointed outhereinafter and set forth in the appended claims constituting part ofthe application.

In the accompanying drawing a preferred embodiment of the invention isshown by way of illustration and not by way of limitation.

In the drawing:

FIG. 1 is a longitudinal cross section of a circuit breaker according tothe invention, and

FIG. 2 is a circuit diagram of a tracer assembly including the circuitbreaker.

Referring first to FIG. 1 in detail, the exemplified circuit breakercomprises a sleeve formed of two parts and 21 suitably secured together,for instance by a screw connection. Sleeve part 20 includes a holder 22for an electric igniting device 23 of conventional design. The device isconnected to conductor wires 24 and 25 which should be visualized asleading to a suitable source of current. A pyrotechnical charge 26 ofsuitable and conventional composition is fitted into sleeve part 20 incoacting relationship with igniter 23 so that the charge will be ignitedwhen the igniter is activated.

Sleeve part 21 houses two terminal contacts 28 and 29 in the form ofmetal pins which are secured in the sleeve part by suitable means suchas an insulation plug 27. The two pins lead to conductor wires 28a and29a which should be visualized as being connected to a control circuit.The two pins 28 and 29 are bridged by a frangible conductive bridge 30formed for instance by thin metal wires.

A plunger 31 of insulation material is slidably fitted in sleeve part 21between the charge 26 and the bridged end of pins 28 and 29. A frangibledisk 32 of insulation material is preferably interposed between the pinsand the 3,277,255 Patented Oct. 4, 1966 adjacent face of the plunger fora purpose which will become more fully apparent from the subsequentdescription. The end face of the plunger facing the pins includes anannular recess 33 to define a central lug 34.

As it is evident, the plunger will be retained in its position in anyposition of the circuit breaker and also when the circuit breaker issubjected to jars. However, when the charge 26 is ignited by activatingigniter 23, the there by generated pressure force will drive the plungertowards the right as seen in the figure. As a result, disk 32 will befractured and the central lug 34 will break bridge 30. Recess 33 willaccommodate pins 28 and 29 when the face of lug 34 moves past thelocation of bridge 30.

Turning now to FIG. 2, this figure shows a circuit system forselectively igniting one or four tracers in a rocket type missile orsimilar Weapon.

The rocket type missile, which should be visualized as beingconventional and is not shown, comprises a battery 35 which is activatedby suitable and conventional means (not shown) when the missile islaunched. The battery serves to supply current for the entire mechanismof the missile but only those circuit components of the mechanism whichare essential for the understanding of the invention are included in thecircuit diagram. More specifically, the tracer assembly is shown and, inparticular, the electric igniters 36, 37, 38 and 39 tor the tracers.Igniter 39 is connected across the terminals of the battery throughlines 40, 41 and 43. An initially open switch 42 is connected betweenlines 41 and 43. Igniters 36, 37, and 38 are connected to line 41through a line 44 and also to line through a circuit breaker R of thekind shown in FIG. 1. The bridge 30 of FIG. 1 is symbolized in FIG. 2 bya switch 45 and the igniter 26 of FIG. 1 is symbolized by the symbol 46in FIG. 2. Igniter 46 is connected to one terminal of the batterythrough lines 47 and 40 and to the other terminal through lines 48 and51. Lines 48 and 51 are connected by a selector switch 49. The selectorswitch may be visualized as being part of a stationary control device 50which is suitably connected with the missile.

If the selector switch is in its open position, as shown in FIG. 2, nocurrent can fiow through igniter 46 when battery 35 is activated whenthe missile is launched and accordingly switch 45 remains closed whenthe missile is launched. In this connection it should be understood thatthe connection between the missile and the stationary control device 50through lines 48 and 51 is automatically broken in a conventionalfashion after the missile is launched.

When now switch 42 is closed after a predetermined flight time of themissile by any suitable mechanical, electric or electronic means ofconventional design, or also after a predetermined time, the igniters 36through 39 for all four tracers are connected to the battery andaccordingly all four tracers will be ignited.

It selector switch 49 is closed prior to the launching of the missile anenergizing circuit will be established through igniter 46 the momentbattery 35 is activated as previously described whereby the circuitbreaker opens switch 45. As a result the connection to igniters 36, 37and 38 is interrupted at switch 45 so that closing of switch 42 aspreviously described establishes an energizing circuit for igniter 39only and accordingly the tracer associated with igniter 39 is the onlyone which will be ignited.

While the invention has been described in detail with respect to acertain now preferred example and embodiment of the invention, it willbe understood by those skilled in the art after understanding theinvention, that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention, and it is intendedtherefore to cover all such changes and modifications in the appendedclaims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A circuit breaker comprising a tubular housing, two terminal contactsconnectable to a control circuit and fixedly mounted in said housing, afrangible conductor bridging said terminal contacts, an actuating membermovable in said housing from an inactive position separated from saidterminal contacts into a circuit breaking position, said actuatingmember including a plunger slidable in said housing along a pathintersecting the position ocupied by said bridging conductor and havingin its end face facing said terminal contacts an annular recess defininga central lug, said lug being engageable with said bridging conductor soas to fracture the same and said recess receiving the terminal contactswhen and while the lug is moving towards its circuit breaking position,a pyrotechnical charge disposed in said housing adjacent to the end faceof the plunger opposite the recessed face thereof, and an activatingmeans for igniting said charge, the pressure generated upon ignition ofthe charge in said housing causing movement of the actuating member intoits circuit breaking position.

2. A circuit 'breaker comprising a tubular housing, two terminalcontacts connectable to a control circuit'and fixedly mounted in saidhousing, a frangible conductor bridging said terminal contacts, anactuating member lengthwise movable in said housing from an inactiveposition separated from said terminal contacts into a circuit breakingposition in which the actuating member causes fracturing of saidbridging conductor, a pyrotechnical charge disposed in said housing onthe side of the actuating member remote from said terminal contacts, afrangible partition wall in the housing interposed between said terminalcontacts and said actuating member to prevent accidental displacement ofthe latter into its circuit breaking position, and an activating meansfor igniting said charge, the pressure generated upon ignition of thecharge in said housing causing movement of the actuating member into itscircuit breaking position.

References Cited by the Examiner UNITED STATES PATENTS 2,929,892 3/1960Blomgren 200-61.08 X

BERNARD A. GILHEANY, Primary Examiner.

R. N. ENVALL, 11s., Assistant Examiner.

2. A CIRCUIT BREAKER COMPRISING A TUBULAR HOUSING, TWO TERMINAL CONTACTSCONNECTABLE TO A CONTROL CIRCUIT AND FIXEDLY MOUNTED IN SAID HOUSING, AFRANGIBLE CONDUCTOR BRIDGING AND TERMINAL CONTACTS, AN ACTUATING MEMBERLENGTHWISE MOVABLE IN SAID HOUSING FROM AN INACTIVE POSITION SEPARATEDFROM SAID TERMINAL CONTACTS INTO A CIRCUIT BREAKING POSITION IN WHICHTHE ACTUATING MEMBER CAUSES FRACTURING OF SAID BRIDGING CONDUCTOR, APYROTECHNICAL CHARGE DISPOSED IN SAID HOUSING ON THE SIDE OF THEACTUATING MEMBER REMOTE FROM SAID TERMINAL CONTACTS, A FRANGIBLEPARTITION WALL IN THE HOUSING INTERPOSED BETWEEN SAID TERMINAL CONTACTSAND SAID ACTUATING MEMBER TO PREVENT ACCIDENTAL DISPLACEMENT OF THELATTER INTO ITS CIRCUIT BREAKING POSITION, AND AN ACTIVATING MEANS FORIGNITING SAID CHARGE, THE PRESSURE GENERATED UPON IGNITION OF THE CHARGEIN SAID HOUSING CAUSING MOVEMENT OF THE ACTUATING MEMBER INTO ITSCIRCUIT BREAKING POSITION.